Cooling unit for refrigerating machines



March], 1938. L. w. ATCHISON COOLING UNIT FOR REFRIGERATING MACHINES 2Sheets-Sheet 1 Filed NOV. 27, 1935 Fig.1.

Inventor: Leonard Wjtchison, '=l 0. M

is AttoThey.

March 1, 1938. w c -uso 2,109,986

COOLING UNIT FOR REFRIGERATING MACHINES Filed Nov. 27, 1935 2Sheets-Sheet 2 Fig.5.

4 zc 23 24 mm...

I n 7 1 w I I Inventor:

Leonard \M Atchison,

is Attorney.

Patented Mar. 1, 1938 UNITED STATES COOLING UNIT FOR BEFBIGERATINGMACHINES Leonard W. Atchison, Schenectady, N. Y., assignor to GeneralElectric Company. a corporation of New York Application November 27,1935, Serial No. 51,846

My invention relates to healing units or evaporators for refrigeratingmachines.

This application is a continuation in part of my application Serial. No.7,683, filed February 23, 1935, and assigned to the General ElectricCompany, assignee of this present application.

It is an object of my invention to provide a simple and improved coolingunit or evaporator of the flooded type for refrigerating machines havinga plurality of surfaces for supporting freezing trays or the like, whichshall afford an efficient circulation of liquid refrigerant, and whichshall be easy to manufacture.

Another object of my invention is to provide a sheet metal evaporatorhaving an improved freezing surface affording high heat absorbingcapacity.

Further objects and advantages of my invention will become apparent asthe following description proceeds, and the features of novelty whichcharacterize my invention will be pointed out with particularity in theclaims annexed to and forming a part of this specification.

For a better understanding of my invention reference may be had to theaccompanying drawings, in which Fig. 1 shows a household refrigeratorutilizing an evaporator embodying my invention; Fig. 2 is an enlargedperspective view of the evaporator shown in Fig. 1; Fig. 3 is a planview of the sheet metal portions of the evaporator shown in Fig. 1 priorto bending. Fig. 4 is an enlarged sectional view on the line 44 of Fig.3; Fig. 5 is an enlarged view of a portion of the conduit shown insection in Fig. 4 showing the distribution of refrigerant therein andFig. 6 is a front elevation of a cooling unit including two evaporators,such as the one shown in Fig. 1.

Referring to the drawings, in Fig. 1 I have shown a householdrefrigerator comprising a cabinet Ill having a food compartment II and adoor l2 for closing the compartment. The compartment ii is cooled by anevaporator or cooling unit I3 arranged in the upper portion thereof andsupplied with refrigerant from a refrigerating machine mounted on thetop of the cabinet. The refrigerating machine comprises a closed casingit in which is arranged a motor and a compressor, an air cooledcondenser i5 having a conduit I6, and a float valve chamber I1. Duringoperation of the motor and compressor within the casing i4, refrigerantis compressed and discharged into the conduit I6 of the condenser i5where it is cooled and liquefied, and then flows through a connection Hito the float valve chamber l1. When a predetermined amount of liquidrefrigerant has collected in the float valve chamber ll, a floatarranged therein rises and admits refrigerant through a conduit IE tothe evaporator iii. The liquid refrigerant is vaporized by the absortion of heat from the chamber H and the vapor col-- lects in acylindrical header 20 from which it is withdrawn through a. conduit 2!and is returned to the casing M. This cycle of operation continues aslong as the compressor within the casing is operating. The temperaturewithin the compartment II is regulated thermostatically in the usualmanner by controlling the operation of the motor which drives thecompressor within the casing M.

It is desirable to provide an evaporator which shall have a plurality ofsurfaces on which freezing trays or the like may be supported, and whichshall provide an efficient circulation of liquid refrigerant in orderrapidly to freeze the water or food within the trays. Furthermore, it isdesirable that the evaporator be of simple construction. I attain theseadvantages by constructing the evaporator of two sheets of metal havingindentations formed therein and shaped to provide adequate surface forcooling the air in the compartment and a plurality of surfaces forsupporting freezing trays and the like. The indentations are arranged toform a header and a plurality of depending U-shaped refrigerantcirculating passages or conduits wherein liquid refrigerant may berecirculated, and a sinuous passage or conduit for supplying refrigerantto the depending passages and for producing a circulation of refrigeranttherein. Portions of the refrigerant passages are arranged in thefreezing tray supporting surfaces so as to provide for the absorption ofheat from the freezing trays and the like.

Referring now to Fig. 2, the evaporator I3 is made of inner and outersheet metal portions,,

which in the construction shown comprise inner and outer sheets 22 and23 respectively. The sheets 22 and 23 are made of stainless steel orother suitable material and are provided with indentations orcorrugations forming the cylindrical header 20 adjacent the upper endsof the sheets, a plurality of depending u-shaped passages or conduits25, each communicating at both ends with the lower portion of theheader, a sinuous conduit 26, a manifold 21', and a plurality of ducts28 connecting the manifold 21 and the lower portion of each of theU-shaped passages 25. The sheets 22 and 23 are bent to form side walls28 and 30 of the evaporator, and top and bottom walls 3| and 32respectively providing upper and lower surfaces 3la and 32a forsupporting freezing trays and the like. The depending U-shaped passages25 extend downwardly from the header 20 within the side wall 29 andacross the bottom wall 32, and the sinuous conduit 26 extends in partacross the top wall 3! and in part within the side wall 30. The sheets22 and 23 are secured together around their edges and between theindentations by welding, brazing, or in any other suitable manner, thefront and rear edges of the sheet 22 being folded over the edge of thesheet 23, as shown at 2i. A flange 33 formed on the sheet 22 and at theend thereof remote from the header flts against the side wall 29 and iswelded or otherwise secured thereto. A metal sheet 34 is welded to theupper end of the side wall 30 and constitutes a side wall for an upperfreezing chamber. The wall 29 and the wall 34 are provided with flanges35 and 36 respectively, for securing the evaporator to a removable topwall of the refrigerator cabinet. The arrangement of the header andpassages within the walls of the evaporator is clearly shown in Fig. 3.

In constructing the evaporator shown in Fig. 2, the outer sheet 23 iscut and stamped while flat as shown in Fig. 3. One side of the header20, the U-shaped passages or conduits 25, the manifold 21, ducts 28, apassage 31, and the portions of the sinuous conduit 28, which are to liewithin the side wall, are formed in the outer sheet 22. The inner sheet22 is cut and stamped while flat so as to provide the other half of theheader 2l| and the indentations forming the portion of the sinuousconduit 26, which is to lie within the top wall at, these indentationsbeing clearly shown in dotted lines in Fig. 3. The two sheets 22 and 23are then secured together face to face. and are welded together aroundthe edges and between the indentations so as to form a pressure-tightand fluid-tight evaporator, and the edges of the sheet 22 are foldedover the opposite edges of the sheet 23, as indicated at 24 in Fig. 2.The flange 33 is formed at the end of the sheet 22 remote from theheader 2|! and the flange 25 is formed at the other end thereof and thesheets are bent to form the evaporator shown in Fig. 2, the sheet 23being the outside sheet. The bends are so located that the U-shapedpassages 25 lie within the side wall 29 and the bottom wall 22, and sothat the manifold 2! lies along the corner between the bottom wall 22and the side wall 20. The top wall 3i extends from the wall 30 towardthe wall 29 and the flange 23 is welded to the wall 29 thereby formingan enclosed freezing chamber in the lower portion of the evaporatorbetween the top and bottom walls 3| and 32. After the sheets 22 and 23have been formed in this manner, the wall 84 is welded or otherwisesecured to the top of the wall 20 to complete the evaporator and to forman upper freezing chamber. It will be noted that the indentations in thesheet 22 lie on the outside of the evaporator, and the indentations inthe sheet 22 lie on the lower side of the top wall 3|; both freezingtray supporting surfaces are thus made flat to give good heat exchangecontact, and further, a flat surface is provided for the welding of theflange 82 to the side wall 28.

All the refrigerant which is supplied to. the evaporator must passthrough the sinuous conduit 20 before reaching the manifold 21 and thecirculating passages 25 since the sinuous conduit is in series betweenthe supply conduit l8 and the manifold. During normal operation of therefrigerating machine, refrigerant flows through the passage 20 at asubstantially constant rate, that is, the pounds of refrigerant passingtherethrough per second do not change. I have found that thecross-sectional area of {the conduit 26 should be proportioned withrespect to the normal rate of flow therethrough so that the vaporizedrefrigerant which flows at a relatively high velocity forces the liquidrefrigerant in the conduit toward all the interior surfaces thereof.when the conduit is proportioned to give this characteristic ofoperation, as shown in Fig. 5, the vapor 26a flows through the center ofthe conduit and the liquid 26b flows in an envelope about the vapor inintimate contact with the interior of the conduit and the entireinterior surface is maintained wet with liquid refrigerant therebygreatly increasing the heat absorbing capacity of the conduit. In Fig.5, for purpose of illustration, the vaporized refrigerant has been shownas having a cross-section of smooth periphery. It should be understood,however, that there is turbulence of the liquid refrigerant and thatdrops or waves of liquid may be present in the vapor stream. However, ifthe velocity of the refrigerant is sufficiently high a layer of liquidrefrigerant will be maintained on all of the interior surfaces of theconduit. If the velocity is too low the upper side of the conduit willbe dry except for the occasional splashing of liquid due to the waveaction along the conduit. The effective heat absorbing surface is alsoincreased by making the conduit thin and flat so that from to 55 percent or substantially one half of the surface of the conduit lies in thefreezing tray supporting surface adjacent any articles placed thereinfor cooling. Highly efllcient operation under normal conditions forhousehold refrigerating machine evaporators will be obtained when thedepth of the conduit 26 is made between 20 and '75 thousandths of aninch, depending on the capacity of the machine and the refrigerant used,the width of the conduit, the mean or average width when the width isvariable as in Fig. 5, being between five and nine times the depth. Thefigures given are only illustrative of depths and widths that have beenused in evaporators of the construction shown in Fig. 2, and do not fixany definite cross sections. Those skilled in the art will determine thearea of the cross section suitable for any particular construction,capacity and refrigerant, by tests of different cross sections under theconditions with which they are dealing. This construction provides afreezing shelf or other evaporator surface having a high heat absorbingcapacity even when the evaporator is constructed of a material such asstainless steel which has areiatively low coeflicient of thermalconductivity. It will be observed that the conduit 25 is a conduit ofthe non-flooded type. The distribution of the liquid refrigerant overthe entire inner periphery of an evaporator conduit of the non-floodedtype is especially useful in the case of a horizontal conduit and thisis particularly the case where a horizontal conduit is made of arelatively poor heat conductor such as stainless steel.

Referring now to Figs. 2 and 3, liquid refrigerant is admitted to theevaporator I I through the conduit [9, enters the passage 21, and flowsinto the sinuous passage 26 through which it circulates and from whichit flows into the manifold 21. Refrigerant from the manifold 21 flowsthrough the ducts 28 and into the lower portion of the dependingU-shaped passages or conduits 25 in which the refrigerant induces acirculation, the refrigerant circulating up one side of each of thepassages 25 into the header and from the header down the other sides ofthe passages. Gaseous refrigerant is withdrawn from the header above thelevel of liquid refrigerant therein through the conduit 2|. In thismanner the walls of the evaporator produce adequate refrigeration tocool the air in the food compartment of the cabinet, and freeze articleson the surfaces lie and 22a.

Refrigerant, which is vaporized in the sinuous passage 26, increases thepressure in the passage and forces refrigerant from the manifold 21 andthrough the ducts 23 into the U-shaped passages or conduits 25. Thisflow of refrigerant will take place even though refrigerant is not beingsupplied to the evaporator from the float valve chamber H, as long asheat is being absorbed by the evaporator and is vaporizing refrigerantin the sinuous passage 26. The liquid and gaseous refrigerant enteringthe U-shaped passages 25 will produce a circulation therein which willassist the thermally induced circulation in the passages in eitherdirection of flow. This arrangement whereby the U-shaped passages areprovided with ducts for admitting refrigerant at the lower ends thereofis not my invention, but is the invention of Delbert F. Newman, and isdescribed and claimed in his copending application Serial No. 3,651,riled January 26, 1935, now Patent No. 2,060,633, granted November 10,1936, and assigned to the General Electric Company, assignee of mypresent invention.

It is sometimes desirable to provide a larger capacity cooling unithaving additional surfaces for supporting freezing trays and the like,and for cooling the compartment in which it is used. In order toaccomplish this, I secure together side by side two evaporators of thetype shown in Figs. 1 and 2 and described above. An equalizer conduit oflarge diameter is provided to connect the headers and to maintain thesame level of liquid refrigerant in both evaporators, and also toequalize the pressures therein. A large capacity cooling unitconstructed in this manner is shown in Fig. 6 and comprises evaporators38 and 39 which are each of the construction shown in Figs. 1, 2, 3, 4and 5, the evaporator 33 being of greater width than the evaporator 38.The evaporators 38 and 39 are provided with supporting flanges 40 and iirespectively above the headers of the evaporators, and with supportingflanges 42a and 430. on extended side walls 42 and 43 respectively onthe sides of the evaporators remote from the headers, and the coolingunit may be secured in a refrigerator cabinet by connecting theseflanges to the top wall of the cabinet. Liquid refrigerant is admittedto the cooling unit through a conduit 44 and to the evaporators 3a and39 through connections 45 and 46 respectively. Headers 41 and 48 of theevaporators 38 and 33 respectively are provided with an equalizerconnection which in this construction comprises a conduit or tube 49 ofrelatively large diameter which connects the headers at the level ofliquid refrigerant and equalizes the liquid levels in the evaporators,and also the gas pressures therein. Gaseous refrigerant is withdrawnfrom the cooling unit through a suction connection 5|) communicatingwith the header 48 above the level of liquid refrigerant therein. Duringoperation of the cooling unit shown in Fig. 6 there is a rapidcirculation of refrigerant throughout the passages within the surfacesfor supporting the freezing trays, and a large tray supporting area isavailable to freeze ice, desserts, or the like. Furthermore, a largearea for cooling the air within the cabinet is provided. It will beunderstood that the circulation of liquid refrigerant in the evaporators33 and 39 is the same as that described in connection with Figs. 2 and3, except that liquid refrigerant may flow between the evaporators andthe gaseous refrigerant is withdrawn only from the header 39.

While I have shown and described my invention as applied to anevaporator for household refrigerators, other applications will readilybe apparent to those skilledin the art, I do not, therefore, desire myinvention to be limited to the particular construction shown anddescribed, and I intend in the appended claims to cover allmodifications within the spirit and scope of my invention.

What I claim as new and desire to secure by Letters Patent in the UnitedStates is:

1. A flooded evaporator for refrigerating machines comprising a headerfor containing liquid refrigerant, a plurality of separate U-shapedrefrigerant circulating conduits depending from said header, each ofsaid U-shaped conduits communicating at both ends with said header belowthe normal liquid level of the refrigerant therein, means including saidU-shaped conduits for providing a side wall of said evaporator and asurface for supporting freezing trays and the like, means for supplyingrefrigerant to said U-shaped conduits and for producing a circulation ofrefrigerant in said U-shaped conduits, means including a sinuous conduitcommunicating with said circulation producing means for providing asecond wall of said evaporator and another surface for supportingfreezing trays, means for supplying refrigerant to said sinuous conduit,and means for withdrawing gaseous refrigerant from said header.

2. A flooded evaporator for refrigerating machines comprising sheetmetal portions joined together about their edges and forming two sidewalls and top and bottom walls of a freezing chamber, said top andbottom walls having surfaces for supporting freezing trays and the like,a header formed between said sheet metal portions above said top wall, aplurality of U-shaped refrigerant circulating conduits communicating atboth ends with said header, said U-shaped conduits extending betweensaid sheet metal portions in one of said side walls and in said bottomwall, a sinuous conduit extending between said sheet metal portions inthe other of said side walls and in said top wall, means for supplyingliquid refrigerant to said sinuous conduit, a manifold communicatingwith said sinuous conduit and extending between said sheet metalportions near said bottom wall, means including a plurality of ductsconnecting said manifold and said Ushaped conduits for injectingrefrigerant into said U-shaped conduits to induce a circulation ofrefrigerant therein, and means for withdrawing gaseous refrigerant -fromsaid header.

3. A flooded evaporator for refrigerating machines comprising two sheetmetal portions joined together about their edges and formed to providetwo side walls and top and bottom walls of a freezing chamber, said topand bottom walls providing an upper and a lower surface for supportingfreezing trays and the like, one of said side walls extending above saidupper supporting surface, a header formed in said one side wall, meansfor securing the edge of said top wall to said one side wall, meansincluding a wall secured to the other side wall of said evaporator forsupporting said evaporator and for providing an upper freezing chambertherein, means including a plurality of conduits formed between saidsheet metal portions and communicating with said header for providingrefrigerant circulating paths within said side walls and within said topand bottom walls, means supplying refrigerant to said evaporator forproducing a circulation of refrigerant in said conduits, and means forwithdrawing gaseous refrigerant from said header.

4. A cooling unit for refrigerating machines including two refrigerantheaders arranged at substantially the same level, means including agroup of depending refrigerant circulating conduits communicating withthe first of said headers and forming a freezing chamber, meansincluding a group of depending refrigerant circulating conduitscommunicating with the second of said headers and forming a secondfreezing chamber, means for supplying liquid refrigerant to each of saidgroups of refrigerant circulating conduits, means including anequalizing connection between said headers for maintaining the samelevel of liquid refrigerant in both of said headers and for maintainingboth of said headers at the same pressure, and means for withdrawinggaseous refrigerant from said cooling unit.

5. Refrigerating apparatus having a thin flat refrigerating conduit ofthe non-flooded type, means for supplying liquid refrigerant to saidconduit and for withdrawing refrigerant from said conduit, thecross-sectional area of said conduit being so proportioned with respectto the normal operating capacity of the means for supplying andwithdrawing refrigerant that the vaporized refrigerant flowing thereinforces the liquid refrigerant flowing therein toward all interiorsurfaces thereof to maintain the entire interior surface of said conduitwet with liquid refrigerant.

6. Refrigerating apparatus having a flooded evaporator having side andbottom walls and comprising a header and a plurality of dependingrefrigerant circulating conduits communicating therewith, meansincluding a thin fiat nonflooded conduit for providing a freezing traysupporting shelf between said side walls, means for supplying liquidrefrigerant to said shelf conduit and for withdrawing vaporizedrefrigerant from said header, said shelf conduit having a crosssectionalarea so proportioned with respect to the normal operating capacity ofthe refrigerant supplying and withdrawing means that the vaporizedrefrigerant flowing therein forces the liquid refiigerant flowingtherein toward all interior surfaces thereof to maintain the entireinterior surface of said shelf conduit wet with liquid refrigerant, andmeans connecting said shelf conduit and said depending conduits forsupplying refrigerant to said depending conduits and for producing acirculation of refrigerant therein.

'7. A flooded evaporator for refrigerating machines comprising sheetmetal portions joined together about their edges and forming a coolingsurface, said sheet metal portions having formed therein a header and aplurality of depending refrigerant circulating conduits eachcommunicating at both ends with said header, a sinuous conduit formedbetween said sheet metal portions, means for supplying liquidrefrigerant to said sinuous conduit, means providing communicationbetween said sinuous conduit and said refrigerant circulating conduitsfor injecting refrigerant into said refrigerant circulating conduits andfor producing a circulation of liquid refrigerant in said refrigerantcirculating conduits, and means for withdrawing gaseous refrigerant fromsaid header.

8. Refrigerating apparatus having a refrigerating conduit of thenon-flooded type and means for supplying a vaporizabie liquidrefrigerant thereto and withdrawing the vaporized refrigerant therefrom,the area of the cross section of the conduit being so small with respectto the normal operating capacity of the means for supplying andwithdrawing the refrigerant as to cause the refrigerant to flow in theconduit with a velocity so high that the liquid refrigerant will coverthe entire inner surface of the conduit and completely enclose thevaporized refrigerant throughout a substantial portion of the length ofthe conduit.

9. Refrigerating apparatus having a refrigerating conduit of thenon-flooded type and means for supplying a vaporizable liquidrefrigerant thereto and withdrawing the vaporized refrigerant therefrom,the area of the cross section of the conduit being so small with respectto the normal operating capacity of the means for supplying andwithdrawing the refrigerant as to cause the refrigerant to flow in theconduit with a velocity so high that the liquid refrigerant will coverthe entire inner surface of the conduit and completely enclose thevaporized refrigerant throughout substantially the entire length of theconduit.

10. Refrigerating apparatus having a refrigerating conduit of thenon-flooded type comprising a horizontal portion, means for supplying avaporizable liquid refrigerant to said conduit and for withdrawing thevaporized refrigerant therefrom, the area of the cross section of saidhorizontal portion being so small with respect to the normal operatingcapacity of the means for supplying and withdrawing the refrigerant asto cause the refrigerant to pass through said horizontal portion of theconduit with a velocity sufficiently high to cause liquid refrigerant tocover the entire inner surface of the horizontal portion of the conduitand enclose the vaporized refrigerant for substantially the entirelength of said horizontal portion.

11. Refrigerating apparatus having a refrigerating conduit of thenon-flooded type composed of a material of relatively low heatconductivity, and means for supplying a vaporizable liquid refrigerantthereto and for withdrawing the vaporized refrigerant therefrom, thearea of the cross section of the conduit being so small with respect tothe normal operating capacity of the means for supplying and withdrawingthe refrigerant as to cause the refrigerant to flow in the conduit witha velocity so high that the liquid refrigerant will cover the entireinner surface of the conduit and completely enclose the vaporizedrefrigerant throughout substantially the entire length of the conduit.

12. A household refrigerator having a refrigerating conduit of thenon-flooded type comprising a horizontal portion made of a relativelypoor conductor of heat, and means for supplying a vaporizable liquidrefrigerant to said conduit and for withdrawing the vaporizedrefrigerant therefrom, the area of the cross section of the horizontalportion of said conduit being so small with respect to the normaloperating capacity of the means for supplying and withdrawing therefrigerant as to cause the refrigerant to flow in said horizontalportion with a velocity so high that the liquid refrigerant will coverthe entire inner surface thereof and completely enclose the vaporizedrefrigerant throughout substantially the entire length thereof.

LEONARD W. ATCHISON.

